Weather forecast goes global

Regional weather forecasting models focus on targeted areas, from river
basins to continents, at resolutions high enough to depict individual
storms and other fine-scale features. Weather doesn’t stop at the
edge of a model’s domain, however. The artificial boundaries between
regions can create forecasting problems.

This animation (see “On the Web” for a link to the live version)
illustrates one approach to solving the artificial boundary problem:
targeting the entire planet instead of just one region. NCAR researchers
are testing the ability of a regional weather model (the advanced research
version of the Weather Research and Forecasting model) to stretch to
the global scale.

The 10-day forecast shown in the animation starts with observed
conditions on July 12, 2007, at 8:00 a.m. Eastern Daylight Time. The
fine-scale details in emerging fronts and storms are visible as water
vapor circulates in the atmosphere. Several tropical depressions on either
side of the Pacific Ocean grow into full-fledged tropical cyclones. The
model captures, for example, the passage of Supertyphoon Man-Yi
as it rolls over Japan’s southern islands and sweeps north.

Calculating the evolution of temperature, humidity, pressure,
and other key data on a three-dimensional grid requires considerable
computing power. This experiment used data points about
30 miles (50 kilometers) apart, a resolution typical of the
global weather prediction models used by operational forecasters.
Test forecasting at 12 mi (20 km) is under way, and the team plans
experimental global runs at even higher resolution.